What is H. pylori?

Helicobacter pylori (H. pylori) is a type of bacteria. Researchers believe that H. pylori is responsible for the majority of peptic ulcers.

H. pylori infection is common in the United States: About 20 percent of people under 40 years old and half of those over 60 years have it. Most infected people, however, do not develop ulcers. Why H. pylori does not cause ulcers in every infected person is not known. Most likely, infection depends on characteristics of the infected person, the type of H. pylori, and other factors yet to be discovered.

Researchers are not certain how people contract H. pylori, but they think it may be through food or water.

Researchers have found H. pylori in the saliva of some infected people, so the bacteria may also spread through mouth-to-mouth contact such as kissing.

source: http://digestive.niddk.nih.gov/ddiseases/pubs/hpylori/index.htm